GB2516271A - Worm gears configuration - Google Patents

Abstract

A worm screw 1 is connected to at least one other worm screw by a flexible joint, e.g. a dual cardan joint 2, to produce a train 10. The train 10 also comprises an axle shaft 3 and bearings 4 housed in trims 5. The worm screws 1 are arranged around and engage with a crown gear (8, fig 3). This provision enables a competition of augmented number of teeth during engagement of worm wheel. The train 10 makes itself useful in crowns (8) wherein their toothing is miniature rollers because they have little resistance to workload, thus improving efficiency. The train 10 enables the use of crowns (8) with partial toothing without compromising an operating cycle of full rotation. The train 10 allows easy adjustments in settings for zero backlash. The flexible joint 2 may be a flexible shaft comprising steel cable, cords, pliable rubber etc.

Description

"WORM GEARS CONFIGURATION" 1. SCOPE OF THE INVENTION.

The invention describes a configuration for worm gears that increases the capacity of torque on the crown shaft pulled by increasing the competition from engagement. Usually the dimensioning of the toothing module depends on the relationship between the value of the tangential load imposed and the number of threads involved in the contact between the pair of gears. If we decrease the module of toothing, we can reduce the scaling of machines and also expand its capacity of reduction by restricting the lead angle of its thread. An application if there is especially useful in the crowns with teeth assemblies, those constituted by rollers that replace the teeth, and as a consequence, which dispenses lubrication in contacts between the gears. These devices were designed and redesigned for more than a century, without which their use was widespread. Some limiting factors are an obstacle to the advantagcs significant regarding thc cfficicncy mcchanical that thesc machines could offer. We hope that our invention will help to overcome some of the barriers impeding. An interesting characteristic is that we can build crowns with toothing partial, without affecting the operation to a cycle full revolution. Crowns will no longer be fully circular, transforming into pivoted arms in the center, with outposts in circular arc. This represents fewer costs dunng the preparation of the crown. It also represents that machines will become lighter and at the same time more powerful. Other relevant application of the invention is the ease with which we can adjust its configuration by sefting the backlash zero.

2. BACKGROUND OF THE INVENTION:

A worm screw, when meshed into gear, causes great thrust from the input shaft from the tooth of his fillet which must bc absorbed by an effort tangential by the target tooth in thc crown. Two othcr components of force are wasted in terms of useful work. One in the longitudinal direction of the axis of the crown and the second, due to the pressure angle of the toothing, which is orthogonal to the binomial of forces described, promoting the distancing between the axes. We know that the engagement of a cylindrical worm screw is in the ratio 3:2. We can envision that 2 teeth enmesh with 3 teeth of the crown and we say that the competition of the gearing is of 1.5. Thus, the load maximum imposed by cross-section in the profile of the toothing will be calculated by the torque for that the contact pressure is submitted and the module, or even, the thickness of the tooth, on the basis of the material employed, will scale of agreement. One of the ways to increase the capacity of load imposed on these systems is to expanding the total area of contact between the parties that arc conjugated. A system of "enveloping" configures the concave region perimetral the crown, so that the worm screw can pcnctratc in part, an arc of circle excavated in the pcriphcrv of thc disc. The transverse section in cutting view presents a surface increased, in relation to the model without the envelope. In a similar manner, if we have a section in cross-section of the wonn screw, excavated in the fonn of circular arc, we have designed a "double envelopment", thc today we call toroidal worm screw or globoid. This done, the competition will be made through a geater number of teeth meshed and thc total load will be divided into each contact. It is evident that this property will allow greater efforts may be applied to the target torque. The maximum competition for the concept of globoids is in the order of 12 Vo, i.e., a crown with 50 teeth engagcment will show a competitor of 6 teeth. There are disadvantages in the globoids, however. Such gears are of difficult machining, because that the step of advancement required is not rectilinear as in cylindrical spindles. Fillets of a globoid suffer circular scanning variation in its profile, which represents a significant increase in difficulty of implementation. Another problem arises from the fact that the extremes of fillets, i.e. the positioned farther away from the center line of the longitudinal axis, have their diameters increased, in order to give the profile the concavity circular required. The increase of this magnitude causes elevation of relative velocity during the friction of contact, which does increase the wear of components. The increase in competition, however, promotes that the load being divided by the total increased area, reducing the force that focuses on each tooth. Therefore, spindles globoids allows for a reduction in the design by approximation of the axles, as well as larger capacities of torques. We conclude that competition is an important factor for expanding the capacity of load in a machine.

For a long time, over more than a century, it has been thought in using rollers that would make for the toothing. The friction of bearing is much smaller than the friction of slipping and the employment of rollers eliminates the need for lubrication intensive and of cooling required in the conventional systems. Large spending of thermal energy would be avoided. The difficulty lies in the fact that a roller makes punctual contact with the tapered helical wall of worm screw. A miniature roller, as would be necessary in order to assembly for a tooth, has little provision to support large loads. In order to solve this problem, projects predecessors describe a fillet of crown, providing it with a plurality of rollers aligned. However, knowing the practical difficulty of aligning multiple rollers to the point of spreading fairly the loading that originates in this trace conical, we prefer to believe that the best way to ensure the balance of pressure is using only two rollers articulating them in a support center pivot.

And two rollers per fillet in the crown, is limited to the prediction of maximum load desired by some good Designer of the machine. An additional difficulty arises when we tried to adjust the machine to the backlash zero. A roller may not be touched simultaneously by two walls diametrically opposed, as would be expected for the contact with the cavity of the fillet, without gaps. In projects predecessors we have an arrangement iii which the crown has two bands of scrolling, which affect the symmetry of applied forces, as well as reduces the load-bearing capacity into half In other provisions, the worm screw has dual cavity, so that each one touch the first batteiy of rollers in a dircetion of rotation, but touching another battery of rollers in the opposite direction of rotation. This solution linñts the rcduction capacity of the machine because the step angle of worm screw needs to be expanded. Thus, for the sampled assemblies, in the present state of the art, they have not fulfilled the requirements of the alignment, nor had they fulfilled to the requirements of loading and those of the capacity of reduction. Perhaps this is why the toothing as rollers was not circulated until the days of today.

3. SOLUTIONS OF INVENTION: The invention describes a configuration to increase the number of teeth in contact engagement. The increase of competition allows employ crowns significantly smaller for the same torque capacity provided for in machines. The increase of competition allows the construction of machines with higher capacity in the reduction using a crowii of same diameter, because we can employ smaller modules for the toothing. The use of smaller modules allows for smaller gear pieces. In addition to being economically advantageous, this reduces the speed of relative friction, allowing for the use of engines faster. The configuration described in invention allows a complete cycle of an ann with edges circular arc, which replaces a crown conventional by a crown circular sector, reducing costs of manufacture and the weight of machinery. The invention enables the construction of devices composed by rollers in toothing, because competition multiplied splits the load imposed on each tooth. The invention enables that bacldashes zero is adjusted with great ease and accuracy.

4. SUMMARY OF THE INVENTION:

A worm screw thread is engaged with the teeth accommodated on the worm wheel, the smaller the diameter of the gears, the smaller will be the relative speed of slipping during the contact of the toothing. We know that for between lubricated surfaces, slip speed is an important factor and it must operate within an optimal range prc-established. Thus, it seems good that these diameters be of modest dimensions which require that the teeth have small modules. Considering a competition of 6 teeth we can imagine that a provision configured with a globoid worm will be able to engage with a crown having 50 teeth. Envisioning a cylindrical worm screw we would have to compose a setting in which we would use four worm cylindrical whose competition being 1.5 to obtain the same competition viewed in the toroidal worm. This is the line of reasoning that has led to this patent application. If, in some way, employing a clever architecture and economical, we fit in a train made of a plurality of worm screws 1 and flexible shafts, each of which are making contact with the toothing in the crown, we have increased the competition in the enmeshing and found a solution to the questions raised. For both, shape a flexible shaft, articulated, linking some units of the worm screw 1 uniting them through axles 3 provided with gaskets for dynamic coupling. To each interval between two gears, we add a device of dual eardan type or similar. The worm screws 1 are penetrated by axles 3 that are sustained through bearings 4 which will have support on the trims 5, to be fixed on the chassis of the assembly.

A drive shaft 6 is prolonged and communicates with the engine by means of a connector 7 flexible.

The a angle of work maximum recommended for drive shafts is shown by the representation below according to the maximum speed of rotation of the axis of excitation.

Highlighted in the chart is speed (1,000 l5O0 R. P. M. ) X (12 9) in bold, because it is a reference value usually found in machines of engine electrical. The end portion of the train 10 is fixed by means of a trunnion 12 as to admit axial tensioning.

Graphic: 4000 N Z 25O0 0 1 Hil 0 1 2 3 4 5 6 7 8 910111213141516171819202122 Degrees (slope of work angle on drive shafts) The rotation of the shaft driven will be unique along the train 10 flexible. This ensures that thc total torque on the gear ring is computed depending on the sum of the teeth meshed with the crown threads in its plurality, allocated in the vicinity of its perimeter. This setting allows us to choice of smaller modules for the teeth, which in turn, gives us freedom for us to extend the capacity of reduction of a crown with a same diameter. Or, otherwise, we will have smaller crowns for a same capacity reduction and increased loading of torque. The provision of multiple worm screws 1 enables the toothing on the crown being interrupted by intervals blind without which, however, the engagement be omitted during a cycle complete. This suggests we build crowns as sectors of a circular profile, in replacing the conventional crowns completely circular. The increase in competition will allow for the satisfactory using of toothing in projects aimed at great efficiency. The employment of worm screws 1 in multiple units and distinct around the crown, makes it easy to adjust the Zero backlash. First unit can be adjusted to the left for clockwise rotation, while another unit may be set to the right for the counter-clockwise rotation.

The invention is described graphically by means of the following figures:

5. BRIEF DESCRIPTION OF THE DRAWINGS:

1. Worm screw inserted in shaft keyed into dual cardanjoint with bearings and trims.

2. Worm screws iii plural arrangement configuring a train shaft flexible.

3. Flexible shaft apparatus with train of worm screws of competition 3 with one thread, double-jointed eardan with working angle a and crown conventional of large reduction. Total competition is of 15.

Reduction 1:128.

4. Final assembly of two stages with flexible shaft with train of 4 elements of worm screws of competition 3 with one thread, crown and work angles of 12° for motor speed 1,000 RPM with central provision of engine for limiting sequential loss of efficiency in stage two of the reducer. Reduction 1:128 (1) reduction 1st. Total competition is of 12.

5. Final assembly of flexible shaft with train of 2 elements of worm screws of competition 8, one thread, toothing crown partial and work angles of 22.5° for 300 RPM. Reduction 1:80. Total competition is of 8. Alignment in cxclusivc scctor of crown (A) and alignment distributcd (B).

Backlash clearance required.

6. Final assembly of two stages with strap flexible sprain with train of 4 elements of worm screws of competition 8 with one thread, work angles of 22.5° for 300 RPM and reduction 1:80 in the 2nd stage.

Crown gear toothing is partial. If there is backlash, competition is of 16 and efficiency invariable with the direction of rotation. If backlash zero then total competition is of 8 (note: the efficiency varies with the direction of rotation). Alignment in opposition (A) and alignment distributed (B).

7. Final assembly of two stages with strap flexible sprain with train of 4 elements of worm screws of competition 8 with one thread, work angles of 22.5° for 300 RPM and reduction 1:80 in the 2nd stage.

Full threaded toothing crown. If backlash are foreseen, competition is of 32. If backlash is zero competition is of 16. Efficiency remains unchanged with the direction of rotation, with or without backlash.

8. Final assembly of flcxiblc shaft with train of 2 elements of worm screws of competition 8 with one thread, work angles of 22.5° for 300 RPM, reduction 1:80. Crown full allowing adjustment of backlash zero with a zone set to the right (R) and another zone set to the left (L), total competition is of 8 (note: the efficiency varies with the direction of rotation). Alternatively, total competition is of 16 with estimates of backlash (greater than zero) clearance and efficiency remains unchanged with the direction of rotation.

9. Assemble similar to figure 7, but the dual cardan joints were replaced by Thomson® joints, allowing work angles of 45° for high speeds (1,000 RPM or more).

6. DESCRIPTION OF THE EXEMPLARY EMBODIMENTS:

Fig. 1 shows an cxplodcd view of an clement of worm scrcw 1 rcceiving thc introduction of shaft axle 3 allocated by means of two bearings 4 encapsulated, by their turn, inside trims 5.

The axles 3 suffer the coupling of the terminations of dual cardan joints 2 at their ends. This joint is composed of a central piece, the spider, which has four pins with two alignments orthogonally arranged, the pins containing a ring in order to reduce the friction. Each pair of pins aligned fits in the configuration in "U' of each termination. The remaining two pairs of pins on the erossheads interlink the central portion of the joint and, thus, the axle assembly-flange will be prepared in such a way that transmit torques without damage to the rotation transmitted uniformly on the edges. Fig.2 represents a train 10 coupled as a worm screws 1 series plural which thus configured, demonstrates its flexibility of axial rotation in three dimensions of space. The machine is scaled of one of the worm screw I elements assembled onto a device equipped with a crown 8, so that a distance C. D. ( "center distance") is established between the pair of main axles (Fig.3). A drive shaft 6 is built by extension of an axle 3 installed on the worm screw I that will be coupled with the engine shaft through a connector 7. Setting up a succession of elements in series, we will make that a train 10 made of a plurality of worm screws 1 will be interconnected by dual eardan joints 2, and after be allocated around the crown. The precise positioning of each element of the train 10 forming a semicircle will be obtained by correct mounting of trims 5 in the chassis of the set. The ending edge of train 10 has its axle 3 locked by atrunnion 12 as to support axial thrusts. The torque from the engine will propagate through the double-jointed cardan 2. We should consider the employment of dual cardan joints because the output of the central element has no uniform speed, nor its torque is constant, due to the characteristics of a sinusoidal first transmission of a single cardan. For identical axle angle at the inlet and at the outlet in relation to its central portion, we will have the effect sine neutralized by the superposition periodic trigonometric, given the opposition of phases. We have promoted the contact of the train 10 of worm screws 1 with the teeth of the crown 8 gear which will lead to increased competition from toothing. It is important to consider that for each rotational speed input, the system offers some limitations. In examples represented by fig.3 and fig.4 we take a= 121 whereas 1,000 RPM as angular speed at engine. Although Fig.3 presents a fitting built by 5 worms in a series, we could add many other and with this augment the competition even more. There is that if you study, however, the loss of efficiency after passing through each node axial transmission, which would limit the amount of augers to be employed. Fig.4 describes the assembling of an additional pinion in the drive if the shaft is precisely the central element of the train 10. Tn this way, we hope that the loss of efficiency is conditioned to only two elements, and not four, as you'd expect if the engine departs from one extreme of the train 10. It is obvious that we must consider the losses due to the coupling pinion 11 attached to the engine axle by any means, but this setting can be especially useful in reducers of two stages expecting large rates in the reductions (above 1:100 x 1:?). Following the line of one step reducers, we provide examples drawn in Fig.5 for a reduction 1:80 consisting of two wonn screw 1 elements.

By reason of working angle be 22.5° speed of rotation of the engine will be limited up to 300 RPM.

However, nothing would prevent us from using other types of joints that not a cardan shaft. For exaniple, joints type Rzeppa or Bendix permits larger angles in high turns, although the thennal efficiency is a limiting factor. The employment of Thomson@ joints 16 would permit the coupling alignment of phase in perfect transmission turning between the axles, would admit some inaccuracies of assembly, would eliminate the central portion of the dual cardan joint as well as two of their "spiders" (meaning space savings) and would propitiate greater efficiency with minimal losses. What we exempli our drawings with the dual cardan 2 is to show that our configuration are functional even employing the types already consecrated to joints. Fig.5A represents a machine foreseeing clearance in the backlash and the competition is of 8. Note that each worm screw I enmeshes four teeth during the ratio and that the crown 8 was replaced by a toothed crown partially blind, we will call it crown partial 9. In fact, when the crown partial 9 forwards a tooth in its turning, the first screw loses one contact, but the second one gets the same increment. Considering the rotation of the crown that of degrees, the competition is fully deposited in the second screw, and yet there would still have 8 teeth in the enmeshing. Complementing the turning to 90 degrees, the opposite diameter of the crown partial 9 engages in the first screw, restarting a ncw cycle (Fig.5B) which reactivates the gear. The weight and the cost of the machine will be significantly reduced due to the elimination of the material besides the toothing removed from the crown partial 9. This setting is especially useful when we can use spindles manufactured by injection molding. This would be possible in projects involving rolling toothing, free from excessive heat generated by sliding contacts. Being by half the number cut of teeth of a crown, it would bring good economy in the confection of said toothing, without prejudice to the competition. Expected to be a good implementation, the invention niakes useful therefore for aeronautical projects among others. Still based on the idea of crowns partial 9, we developed the concept presented in Fig.6 for reducers of two stages (large reductions). The train 10 open as previous, now acquires a configuration closed in foci of strap. This is why the train shall henceforth be called the band of sprain 13. The effect obtained is that the decrease in efficiency is limited to the 2nd clement, not the 4th. One of intermediate axes receives a transmission clement 14 that is coupled to the engine 15 may be a pinion, a worm crown or a hypoid gear for the reducing. For predicting backlash, then we will have that the competition will be doubled (in the case oftlie figure, will be 16).

For machines with zero backlashes, the competition will be 8 and the advantage of the design will be translated by the economy of toothing presented in crovrn partial 9. Fig.6A shows an engagement radial in opposition and indicates by the letter R, an adjustment for backlash zero to the right of spindles chosen as well as a set L to the left for the other spindles marked. Fig.6B demonstrates the rotation of sonic degrees in crown partial 9, causing an engagement distributed. Unfortunately this configuration (for backlash zero) will present variations in the efficiency index, according to the direction of rotation to be chosen.

The Fig.7 shows configuration similar, but niade with a crown 8 full conventional. The result obtained is that we will have the competition quadrupled in applications with backlash, or duplicated in the applications by providing zero backlashes. This conformation is ideal for machines of larger size rcquiring grcat substance of loadings and magnitude of torques. In this example, the efficiency is invariable with the direction of rotation, in the procedures both with and without backlash.

Fig.8 repeats the configuration of Fig.5 except that we use a crown 8 complete. This time, we can adjust each spindle without order, one to the left (L) and another to the right (R), so as to adjusting the machine foreseeing backlash zero. The competition will be S and the efficiency will depend on the direction of rotation.

We noticed that iii all the assembly settings where the backlash zero is requested, the invention offers great ease to carry out the adjustment, because that each zone is independent of its pair. One fits a spindle to the left as if outside a fitting with backlash, then we take the other spindle aligning it on the right, also as if outside a fitting with backlash. The sum linear of independent adjustments eliminates the existence of backlash clearance.

Finally Fig.9 presents the model of Fig.7 except that the double universal joints were replaced by joints type Thomson 16 allowing work angles be 45 degrees and the system can operate at higher speeds (above 1,000 rpm).

We believe that changes can be made on the fonn, angular divisions, distinct types of joints, numeric alterations regarding the competition. Although the invention has been described in few main variants, it should be understood that modifications may be set forth in the manner, construction, and arrangements in the assembly of parts as long as, nevertheless, the spirit of protection of the scope of this invention remains secure. All such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.

Claims (7)

1. CLAIMS1. Assemble for devices of type worm gears comprising at least a pair of worm screws that are sequentially interconnected through couplings of flexible mobility that communicates mechanically with the teclh on the crown gcar.
2. 2. Assemble as described in claim I comprising a plurality of worm screws which they are interconnected sequentially through the fining of intermediary joints for the transmission of rotation; the connection between the worm screws has flexible mobility and the various components thus assembled pertain to a train that can articulate angularly in three dimensional spaces; the individual axles on each element of the train are affixed to the chassis of the machine by means of bearings that are housed in their trims; the parts arc adjusted so that all worm screws are set tangent to the perimetral surface of the crown and engages with its toothing.
3. 3. Assemble as described in claims previous in which the train presents a configuration closed cyclic, constituting a band of sprain.
4. 4. Assemble as described in claims previous in which at least one of the elements of the train is replaced by a transmission element that will be driven an input traction, powering the revolving band of sprain or open train.
5. 5. Assemble as described in claims previous, such that individual axles on each element of the train are replaced by tiexible shafts that comprehends steel cables, cords, pliable rubber and other such apparatus to replace rigid joints.
6. 6. Assemble as described in claims previous comprising a crown with toothing partial that performs a complete cycle of engagement on the machine due to redundant existence of worm screws.
7. 7. Assemble as described in claims previous comprising certain number of worm screws adjusted for touching the crown in one direction of rotation; worm screws distinct adjusted for touching the worm wheel in the opposite direction of rotation; the total number of worm screws belonging to the train provides an adjustment that results in backlash zero in either direction of rotation.